1. Field of the Invention
The present invention relates to a queue selection method for controlling queue selection in communication performing packet transfer, and a scheduling device which executes the queue selection method, and more particularly to a queue selection method and scheduling device for implementing scheduling a large volume of queues.
2. Description of the Related Art
Recently an enormous amount of packet data flows through communication networks due to the spread of the Internet. To support this expansion of traffic volume, even faster speeds and large capacities are demanded for relay devices, such as routers, constituting communication networks.
Also as communication data increases, traffic concentration of specific contents begin to generate, where traffic control, using such a means as QOS (Quality of Service) is indispensable, to remove the influence on unrelated traffic and to make the flow of packets smooth.
A relay device, such as a router, which is a scheduling device to execute queue selection control of packets, transfers packets while assuring the required quality and bands of packets transmitting QOS.
FIG. 1 is a diagram depicting a conventional queue selection control. The packet to be input is buffered into a plurality of queues 2, and the queue control section 20 reads and outputs the packets from each queue 10 in a predetermined sequence.
In a conventional queue control configuration, several hundreds of (e.g. 192) queues are set in parallel, and one queue is selected from a plurality of queues using the primary encoder and ring counter so that each queue is evenly selected.
Recently as communication traffic increases, higher speeds and larger capacities for queue control are demanded. However merely increasing the number of queues increases the circuit scale accordingly. If the number of queues were increased from the current several hundred to several tens of thousands, circuit scale become enormous, even for only a register which indicates the presence of packets in a queue to enter the primary encoder, which is not practical.